Conjugated linoleic acids (CLA) are a family of at least isomers of linoleic acid found mostly in the meat and dairy products derived fromruminants. CLAs can be either cis- or trans-fats and the double bonds of CLAs are conjugated and separated by a single bond between them.

In healthy humans, CLA and CLNA isomers are bioconverted from linoleic acid and alpha-Linolenic acid, respectively, mainly by Bifidobacteriumbacteria strains inhabiting the gastrointestinal tract, however this bioconversion may not occur at any significant level in those with a digestive disease, gluten sensitivity and/or dysbiosis.

Anticancer properties have been attributed to CLA, and studies on mice and rats show encouraging results in hindering the growth of tumors in mammary (except HER2 breast cancer), skin, and colon tissues.] It has been reported that CLA can up-regulate the tumor suppressor gene PTPRG, and may have anticancer properties.

A European team led by the Swiss scientist Lukas Rist has found that mothers consuming mostly organic milk and meat products have about 50% higher levels of rumenic acid in their breast milk.

According to studies that targeted the effects of conjugated linoleic acid on the belly firmness and fatty acid composition of genetically lean pigs, the supplemental CLA usage had a positive effect on the improvement of belly firmness and may provide a nutritional solution to carcass fat and belly firmness problems.

The most promising science around CLA concerns its effect on weight management. Thirty-five intervention studies have been conducted using CLA in humans to investigate the effects of CLA on weight management. These studies, which vary widely in CLA dose and duration, show the most significant effect of CLA on weight management is on body composition, a reduction in total body fat and an increase in lean body mass. The effect of CLA on fat mass is modest and at the recommended dosage of 3.2 g/day produces a statistically significant 90 g fat loss per week (about 1 lb in 5 wk) as shown by a 2007 meta-analysis.Doses higher than the recommended 3.2g do not seem to have any additional effects on body fat reduction.

Another meta-analysis found that CLA supplementation produces about 1% increased growth in targeted lean body mass per week With the simultaneous decrease in fat mass coupled with increases in lean body mass, often the net change in weight is small. However, the effects of CLA on body composition is a healthy effect, since the degree of fat mass is related to many causes of mortality and lean body mass burns more calories than fat mass, which may help to increase resting metabolic rates. CLA use itself is not an answer to the prevalence of obesity, but it can be a useful tool in addition to a healthy lifestyle and exercise program to achieve and maintain a healthy body weight.

Some studies have found no significant effects of CLA supplementation on fat mass loss.CLA has also been used in combination with other ingredients which may skew results.